And the description of certain bad things that had happened years before sounded ridiculous as a gloomy speech. It wouldn't have been ridiculous as either flashbacks or a prologue. I would have chosen intrusive chaotic flashback-memories.
I think modern audiences are quite happy to jump in and work things out as they go. British TV execs always underestimate the sophistication of the viewing public, and perhaps particularly how comfortable they are to dive into an SF story, without having every detail explained. Of course there are pedants who want every fact filled in, but most people are happy to wing it.